HVAC systems are used to regulate environmental conditions within an enclosed space. Typically, HVAC systems have a circulation fan that pulls air from the enclosed space through ducts and pushes the air back into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling, humidifying or dehumidifying the air). To direct operations of the circulation fan and other components, each HVAC system includes at least one HVAC controller. Traditionally, the circulation fans in HVAC system were single speed fans that operate in response to an on/off signal from the controller. Some HVAC systems, however, include a variable-speed circulation fan that is controlled by a pulse width modulated signal (PWM) from the HVAC controller.